Per- and polyfluoroalkyl substances remediation

ABSTRACT

The present invention relates to reduction of per- and polyfluoroalkyl compounds (PFAS) in a desired zone of treatment for the continuous remediation of contaminated solids and liquids. In particular, embodiments of the present invention relate to the in-situ treatment of solids and liquids by a particular combination of reagent and conditions. The reagents include an oxidant and a metal catalyst. Disclosed method combines low temperature thermal remediation with chemical oxidation to destroy poly- and perfluoroalkyl substances in-situ. The disclosed methods may enhance destruction of organic contaminants in the desired zone of treatment. The present invention also relates to a method for applying the remediation compositions to contaminated sites and controlling the process by monitoring the degradation event to achieve maximum reduction of PFAS.

RELATED APPLICATION

The present application relates to and claims the benefit of priority toU.S. Provisional Patent Application No. 63/038,282 filed 12 Jun. 2020and U.S. Provisional Patent Application No. 63/145,797 filed 4 Feb.2021, both of which are hereby incorporated by reference in theirentirety for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to compositions and methods for theremediation of contaminated solids and liquids, in particular thein-situ remediation of solids and liquids contaminated by Perfluoroalkylsubstances (PFAS) compounds using an oxidant and a catalyst in a lowthermal environment.

Relevant Background

Perfluoroalkyl substances (PFAS) encompasses a family of thousands ofindividual chemicals used in many industrial and commercial products.PFAS belong to a class of organic chemicals that contain at least onefully fluorinated carbon atom. This moiety is highly hydrophobic andoleophobic resulting in strong water and oil repellent properties. PFASare thus in common use as lubricants in industrial processes and asadditives in insecticides, pharmaceuticals, and aqueous film-formingfirefighting foams. PFAS are also widely used as water and oilrepellents in consumer products, such as carpeting, upholstery, andpaper. As a group, PFAS chemicals are highly resistant to heat, waterand oil, making them highly useful for many industrial applications andconsumer products ranging from non-stick cookware to stain-resistantfabrics. The same chemical properties that make PFAS so effective infirefighting foams and other products make them particularly hard toremediate. Consequently, PFAS degrade very slowly in the environment andthe human body, and contaminated sites are difficult to remediate.

Communities across the country have become concerned about PFASaccumulation and their lack of natural degradation in the environment,and many experts have declared PFAS an emerging major health threat.Known implications of PFAS contamination include negative effects onfetal development, learning and behavior in children, adult fertility,hormonal balance, and/or liver function.

Decomposition of PFAS through biological means have shown limitedtransformation and applicability. A common disposal technique is usingincineration wherein concentrated PFAS stream and some of the PFAS-ladenmaterial is incinerated at temperatures above 1000° C. to undergothermal oxidation. Conventional water treatment technologies have beenassessed for PFAS removal with mixed success. Some of the technologiesexplored include adsorbents, membranes, and advanced oxidationprocesses. A number of conventional sorbents have been explored for PFAScapture but have yet to be validated as a viable commercial means ofremediation. Removal of PFAS can be achieved by activated carbon,inorganic sorbents and ion exchange resins. But what plagues all sorbentprocesses is the need to regenerate or dispose of the exhausted sorbent.

Regeneration may require harmful chemicals or expensive equipment andresults in PFAS being eluted from the sorbent, where they must then bedealt with again. Disposal of the sorbent is wasteful and still risksrelease of PFAS depending on the disposal method. Another strategy is tophysically separate the PFAS using a membrane; reverse osmosis andnanofiltration are examples. However, also like sorbents, they have themain drawback that they fail to destroy the PFAS molecules. As theyremove the PFAS, they create a concentrated stream containing PFAS thatmust be managed.

Previously perfluoroalkyl compounds have been shown to be treated withfine oxygen/ozone gas bubbles delivered with a hydroperoxide coating andsolution activated by high temperature. Ex-situ remediation technologythrough a reactor has been attempted as has an enzyme catalyzedreaction. All the claimed technologies are cumbersome requiring highenergy and complex technologies making the remediation less feasible andcommercially impractical.

The only recognized way to destroy the PFAS is through chemicaloxidation (or mineralization). Chemical oxidation often entails theutilization of oxidants like hydrogen peroxide (HP)(H₂O₂), persulfate(PS)(S₂O₈ ²⁻), and peroxymonosulfate (PMS) (HSO₅ ⁻), but all are knownto be ineffective by themselves to decompose PFAS under ambientconditions. Attention has therefore been given to advanced oxidationtechnologies (AOTs), which utilize strong transient oxidizing speciessuch as hydroxyl radicals (HRs)(.OH) and sulfate radicals(SRs)(SO4SO4.⁻). The HRs can be practically generated under ambientconditions via activation of HP with iron (Fe), commonly known as theFenton reaction. However, the Fenton reaction, proven to work for avariety of persistent organic chemicals, has not yet been reported to beeffective for PFAS in more oxidized forms, such as PFOA and PFOS. Infact, research studies involving AOTs introduced additional workingmechanisms such as photolysis, thermolysis, and sonolysis along with HRand SR mechanisms to decompose PFAS more effectively. They includeH₂O₂/ultraviolet (UV) photo-Fenton, TiO₂/UV photocatalysis, andsonochemical processes for HR generation, as well as S₂O₈ ²⁻/UV, HSO₅⁻/UV, and S₂O₈ ²⁻/microwave for SR generation. PS, one of the mostwidely used oxidants during in-situ chemical oxidation processes, wasreported to require high temperatures at around 60° C.-90° C. todecompose exclusively PFCAs such as PFOA, but PFSAs such as PFOS werenot decomposed even under these conditions. Activation methods for PS byultraviolet, ultrasound, microwave, and/or heat have been attempted. Inspite of their effectiveness, these technologies commonly requireextreme conditions, leading to higher costs and lowering the potentialfor their commercial or even technical viability.

Thus, while various known techniques are available for the reduction ofPFAS compounds, such methods do not generally provide a practical,affordable technology for remediating soil and water sources underambient conditions by using low energy and low cost means of generatinghigh redox potential radicals. These and other deficiencies of the priorart are addressed by one or more embodiments of the present invention.

Additional advantages and novel features of this invention shall be setforth in part in the description that follows, and in part will becomeapparent to those skilled in the art upon examination of the followingspecification or may be learned by the practice of the invention. Theadvantages of the invention may be realized and attained by means of theinstrumentalities, combinations, compositions, and methods particularlypointed out in the appended claims.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a method forremediation of PFAS compounds from a desired zone of treatment, inparticular contaminated soils and water supplies, such as ground waterand other water bodies at ambient or near ambient conditions. It is anaspect of embodiments of the invention to provide a continuous processand system for the in-situ remediation of large-scale contaminated soiland ground water sites that quickly reduce the contaminants toacceptable levels, allowing the resources to once again enter normal useor consumption. The remediation is carried out at ambient ornear-ambient conditions using low energy (ambient energy in many cases)and low-cost means.

One aspect of the present invention is to provide methods for theremediation of large scale PFAS contaminated soil and ground water siteswherein remediation times are on the order of few days to several years.

It is another aspect of embodiments of the invention to providecompositions and methods for the decomposition of PFAS under ambientconditions by using practical technologies for full-scale applications.

Another aspect of embodiments of the present invention is to provide aprocess for in-situ reduction of (PFAS) compounds in a desired zone oftreatment which can be safely regulated and limited based on thedegradation profile of PFAS.

It is one aspect of embodiments of the present invention to provide amethod of generating high redox potential free-radials that couldoxidize PFAS containing carboxylic acids as the functional group, suchas 8:2 fluorotelomer carboxylic acid, 6:2 fluorotelomer carboxylic acid,perfluorooctanoic acid (PFOA), perfluorononanoic acids (PFNA),perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA),perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA),pentafluoropropionic acid (PFPA) and trifluoroacetic acid (TFA) in thedesired zone of treatment.

It is another aspect of embodiments of the present invention to providea remediation formula comprising of a peroxy-based or a sulfur-basedmaterial acting as an oxidant along with a metal acting as a catalystfor the quick generation of high redox potential free-radicals whereinthe molar ratio of catalyst to oxidant is on the order of 1:10-1:250. Inembodiments where an oxidant and metal catalyst are each used, thesecompounds may be used at different molar ratios; for example the molarratio of oxidant to metal catalyst may be 1:10, 1:50, 1:100, 1:150,1:200, 1:250 depending upon Soil Oxidant Demand (SOD). In an embodimentthe results of SOD tests will be used alone or in combination with sitecharacterization data to estimate the quantity and ratio of oxidant andcatalyst.

One aspect of embodiments of the present invention is to provide amethod of treating a desired zone at low thermal environment in thepresence of a metal catalyst and an oxidant. The method includes thesteps of calculating SOD value, which is used to estimate the quantityand ratio of oxidant and metal catalyst, and verifying an ambientin-situ thermal environment within the desired zone of treatment havinga temperature >20° C. If the temperature is <20° C., the desiredtemperature is achieved by injecting hot water or similar sources ofenergy. Once the required low thermal environment is achieved, atransition metal catalyst is injected and dispersed into the ambientin-situ thermal environment creating an ambient in-situ thermal catalystrich environment. Next an oxidant is introduced wherein the catalyst andthe oxidant within the ambient in-situ thermal catalyst rich environmentinteract generating high redox potential free-radicals that oxidize PFAScompounds producing, inter alia, fluoride and carbon dioxide.

An aspect of the present invention includes reacting the oxidant and themetal catalyst in an ambient in-situ thermal environment, wherein thetemperature is ≥20° C. and ≤35° C. or is ≥20° C. and ≤30° C. or is ≥20°C. and ≤40° C. or is ≥20° C. and ≤50° C. or is ≥20° C. and ≤60° C.According to the present invention at temperatures ≥40° C., PFOAdecomposition kinetics are much faster and, as one of reasonable skillin the art will appreciate, PFOA decomposition kinetics are faster astemperature/energy increases. Almost complete decomposition of PFAScompounds can be achieved within hours.

It is one aspect of embodiments of the present invention to provide amethod for the decrease of PFAS compounds using an oxidant along with ametal catalyst wherein the metal catalyst is regenerated after eachcycle of oxidation while the oxidant gets consumed after generating thehigh redox potential free-radicals.

It is an objective of the invention to provide a method for decreasingPFAS mass significantly or appreciably in a treatment zone with no orminimal added energy.

It is a further aspect of embodiments of the present invention toprovide a method wherein the process is monitored and controlled byobserving the concentration of fluoride in groundwater. The amount ofPFAS degraded is assessed by the concentration and the rate of change ofthe concentration of fluoride released into the groundwater. Theinjection of oxidant, and/or catalyst, into the ambient in-situ thermalenvironment is continued until no further increase in fluorideconcentration is observed in groundwater.

It is another aspect of embodiments of the invention to provide a methodto remediate the source area (vadose zone) soils by flushing watercontaining oxidant and catalysts from ground surface downward throughthe vadose zone.

It is another aspect of embodiments of the invention to provide a methodto prevent contamination of groundwater by destroying PFAS compoundswhile they are flushed through the vadose zone.

Yet another aspect of the present invention includes a method ofestablishing the ambient in-situ thermal environment through activeheating generated by mechanical, electrical or chemical sources, orpassive heating through solar heating of the desired zone of treatment.

This brief summary is neither intended nor should it be construed asbeing representative of the full extent and scope of this disclosure.Moreover, references made herein to “the present invention” or aspectsthereof, should be understood to mean certain embodiments and should notnecessarily be construed as limiting all embodiments to a particulardescription. The present invention is set forth in various levels ofdetail in the Summary of the Invention as well as in the DetailedDescription and Examples and no limitation as to the scope is intendedby either the inclusion or non-inclusion of elements, components, etc.in this Summary of the Invention. Additional aspects will become morereadily apparent from the Detailed Description, particularly when takentogether with the examples.

The features and advantages described in this disclosure and in thefollowing detailed description are not all-inclusive. Many additionalfeatures and advantages will be apparent to one of ordinary skill in therelevant art in view of the drawings, specification, and claims hereof.Moreover, it should be noted that the language used in the specificationhas been principally selected for readability and instructional purposesand may not have been selected to delineate or circumscribe theinventive subject matter; reference to the claims is necessary todetermine such inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other features and objects of the presentinvention and the manner of attaining them will become more apparent,and the invention itself will be best understood, by reference to thefollowing description of one or more embodiments taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a schematic flow diagram illustrating components and operationof an PFAS remediation system in accordance with one embodiment of thepresent invention;

FIG. 2A is a perspective view of the area containing high PFASconcentration with proposed injection points for in-situ remediation ofPFAS depicting Step-1 of the process in accordance with one embodimentof the present invention;

FIG. 2B shows Step-2 of remediation of PFAS concentration after initialinjection metal catalyst and oxidant wherein the oxidant is consumed,leaving the metal catalyst in place, in accordance with one embodimentof the present invention;

FIG. 2C shows Step-3, subsequent injection of oxidant to achieve nearcomplete destruction of PFAS in-situ in accordance with one embodimentof the present invention;

FIG. 3 shows a high-level block diagram for PFAS remediation system inaccordance with one embodiment of the present invention;

FIG. 4 is a perspective view of Ex-Situ Reactor for remediation of PFASImpacted Water in accordance with one embodiment of the presentinvention;

FIGS. 5A-5D presents an alternative approach for in-situ surfaceimpoundment and remediation of PFAS vadose zone soils in accordance withone embodiment of the present; and

FIGS. 6A-6D present test data from application of one or moreembodiments directed to remediation of PFAS in accordance with thepresent invention. The Figures depict embodiments of the presentinvention for purposes of illustration only. Like numbers refer to likeelements throughout. In the figures, the sizes of certain lines, layers,components, elements or features may be exaggerated for clarity. Oneskilled in the art will readily recognize from the following discussionthat alternative embodiments of the structures and methods illustratedherein may be employed without departing from the principles of theinvention described herein.

DESCRIPTION OF THE INVENTION

Continuous remediation of per- and polyfluoroalkyl compounds (PFAS) in adesired zone of treatment is hereafter described by way of example. Inparticular, embodiments of the present invention relate to the in-situtreatment of solids and liquids by a particular combination of reagentand conditions. The reagents include an oxidant and a metal catalyst.Disclosed methodology combines low-temperature thermal remediation withchemical oxidation to destroy poly and perfluoroalkyl substancesin-situ. The disclosed methods enhance destruction of organiccontaminants in the desired zone of treatment. The present inventionalso relates to a method for applying the remediation compositions tocontaminated sites and controlling the process by monitoring and therebyactively modifying the degradation event to achieve maximum abatement ofPFAS.

Embodiments of the present invention are hereafter described in detailwith reference to the accompanying Figures. Although the invention hasbeen described and illustrated with a certain degree of particularity,it is understood that the present disclosure has been made only by wayof example and that numerous changes in the combination and arrangementof parts can be resorted to by those skilled in the art withoutdeparting from the spirit and scope of the invention.

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the present invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding, but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Thus, for example, reference to “a component surface”includes reference to one or more of such surfaces.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

It will be also understood that when an element is referred to as being“on,” “attached” to, “connected” to, “coupled” with, “contacting”,“mounted” etc., another element, it can be directly on, attached to,connected to, coupled with or contacting the other element orintervening elements may also be present. In contrast, when an elementis referred to as being, for example, “directly on,” “directly attached”to, “directly connected” to, “directly coupled” with or “directlycontacting” another element, there are no intervening elements present.It will also be appreciated by those of skill in the art that referencesto a structure or feature that is disposed “adjacent” another featuremay have portions that overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of a device in use or operation in addition to theorientation depicted in the figures. For example, if a device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of “over” and “under”. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only unless specifically indicatedotherwise.

As used herein, the term “in-situ” refers to an on-site (action). It isto be understood that in some cases, the disclosed methods may beapplied either in-situ or ex-situ, or a combination or both in-situ andex-situ, depending on the desired application. The followingdescriptions are thus intended to apply to both in-situ and/or ex-situtreatment methods, except as otherwise explicitly stated.

As used herein, the term “PFAS” is used as a general term to representperfluoroalkyl or polyfluoroalkyl substances. Such substances includeperfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA),perfluorooctanesulfonamide (PFOSA), perfluorohexanoic acid (PFHxA),perfluoropentanoic acid (PFPeA), pentafluorobenzoic acid (PFBzA),perfluorobutanoic acid (PFBA), perfluorohexanesulfonic acid (PFHxS),perfluorobutanesulfonic acid (PFBS), perfluorodecanoic acid (PFDA),perfluorododecanoic acid (PFDoA), perfluoroheptanoic acid (PFHpA),perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnA),perfluorononanoic acid (PFNA), hexafluoropropylene oxide-dimer acid(HFPO-DA), perfluoro-2-methoxyacetic acid (PFMOAA),perfluoro-2-mthoxypropionic acid (PMPA), fluorotelomer, or anycombination thereof. In one embodiment, the fluorotelomer comprisesfluorotelomer sulfonate (FTSA) or fluorotelomer carboxylate (FTCA).

As used herein, the term “PFAS-contaminated site” refers to an area ofland that has per- and/or polyfluoroalkyl substances in its surface andsubsurface soils, sediments, aquifer materials, any significantaccumulation of water or water body and/or groundwater.

As used herein, the term “soil” refers generally to any solid or porousmaterial or media that may be contaminated with PFAS and may be treatedaccording to the methods described herein. Soil may comprise naturalinorganic matter and/or bulk natural organic matter. Soil may compriseman-made porous material.

As used here, the term “degrade” refers to breaking one or more chemicalbonds of a substance. One of many openings or void spaces in a solidsubstance of any kind are referred to as pores. Pores are characterizedby their diameters. The term nanopore generally refers to pores havingan average diameter of 100 nm or less.

As used here, the term “GenX” refers to the technologies and chemicalsused to make certain fluoropolymers without the use of perfluorooctanoicacid (PFOA). The technology relies on hexafluoropropylene oxide (HFPO)dimer acid and its ammonium salt. An exemplary GenX compound isundecafluoro-2-methyl-3-oxahexanoic acid (orperfluoro-2-methyl-3-oxahexanoic acid).

As used here, the term “Metal” in a metal catalyst includes Sc, Y, Ti,Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni,Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, In, Ca and mixtures thereof used with orwithout a support material such as zeolite, silica or alumina.

As used here, the term “zone of treatment” refers to an area of landthat has per- and/or polyfluoroalkyl substances in its surface andsubsurface soils, sediments, aquifer materials, any significantaccumulation of water or water body and/or groundwater refers to thearea where PFAS-contaminated soil has been treated or remediated suchthat the level of PFAS contamination in the soil is less than it wasprior to being treated or remediated.

Regulated organic contaminants in the subsurface environment include,but are not limited to: polychlorinated biphenyls (PCBs); chlorinatedvolatile organic compounds (CVOCs), such as tetrachloroethene (PCE),trichloroethene (TCE), trichloroethane (TCA), dichloroethene (DCE),vinyl chloride; fuel constituents such as benzene, ethylbenzene,toluene, xylene, methyl tertbutyl ether (MTBE), tertiary butyl alcohol(TBA), polycyclic aromatic hydrocarbons (PAHs), ethylene dibromide(EDB); pesticides such as (but not limited to) DDT; herbicides such as(but not limited to) Silvex. Pharmaceuticals, personal care products,Endocrine disruptor compounds, aqueous film-forming foam (AFFF),coatings are other products that also may contain highly recalcitrantchemicals and other man-made xenobiotic compounds.

In the interest of clarity, the following terms are further defined.

-   -   By the term PFAS is meant per- and polyfluoroalkyl substances.        PFAS are a group of man-made chemicals that includes PFOA, PFOS,        GenX, and many other chemicals. PFAS have been manufactured and        used in a variety of industries around the globe, including in        the United States since the 1940s. PFOA and PFOS have been the        most extensively produced and studied of these chemicals.    -   By the term PFOA is meant perfluorooctanoic acid. PFOA, also        known as C8, is a man-made chemical. It has been used in the        process of making Teflon and similar chemicals (known as        fluorotelomers). PFOA is considered a surfactant, or        fluorosurfactant, due to its chemical structure, which consists        of a perfluorinated, n-octyl “tail group” and a carboxylate        “head group”. The head group can be described as hydrophilic        while the fluorocarbon tail is both hydrophobic and lipophobic.        The tail group is inert and does not interact strongly with        polar or non-polar chemical moieties; the head group is reactive        and interacts strongly with polar groups, specifically water.        The “tail” is hydrophobic due to being non-polar and lipophobic        because fluorocarbons are less susceptible to the London        dispersion force than hydrocarbons.    -   By the term PFOS is meant perfluorooctanesulfonic acid. PFOS        (conjugate base perfluorooctanesulfonate) is an anthropogenic        fluorosurfactant and global pollutant. PFOS is the key        ingredient in a fabric protector, and numerous stain repellents.        PFOS can be synthesized in industrial production, or it can        result from the degradation of precursor molecules. PFOS levels        that have been detected in wildlife are considered high enough        to affect health parameters, and recently higher serum levels of        PFOS were found to be associated with increased risk of chronic        kidney disease in the general US population.    -   By the term GenX is meant the trade name for a technology that        is used to make high performance fluoropolymers (e.g., some        nonstick coatings) without the use of perfluorooctanoic acid        (PFOA). HFPO dimer acid and its ammonium salt are the major        chemicals associated with the GenX technology. GenX chemicals        have been found in surface water, groundwater, finished drinking        water, rainwater, and air emissions in some areas. As part of        EPA's draft toxicity assessment, EPA has developed draft oral        reference doses (RfDs) for GenX chemicals.    -   By the term remediation is meant the action of remedying        something, in particular of reversing or stopping environmental        damage.    -   By the term groundwater is meant water held underground in the        soil or in pores and crevices in rock.    -   By the term catalyst is meant a substance that increases the        rate of a chemical reaction without itself undergoing any        permanent chemical change.    -   By the term support material is meant an organic or inorganic        material upon or into which the catalyst is embedded and its        exposed to the oxidant to generate the radical species used in        the decomposition process.    -   By the term in-situ is meant situated in the original place. In        the context of the present invention it refers to a clean-up or        remediation of a polluted site performed using processes in the        soil.    -   By the term ex-situ is meant off site. In the context of the        present invention it refers to the remediation of a polluted        site where contaminated soil or water is excavated and cleaned        elsewhere, off site.    -   By the term oxidant is meant an agent (oxidant, oxidizer), or        oxidizing agent (oxidizer) being a substance that has the        ability to oxidize other substances—in other words to accept        their electrons. Common oxidizing agents are oxygen, hydrogen        peroxide and the halogens. In one sense, an oxidizing agent is a        chemical species that undergoes a chemical reaction in which it        gains one or more electrons. In that sense, it is one component        in an oxidation—reduction (redox) reaction. In the second sense,        an oxidizing agent is a chemical species that transfers        electronegative atoms, usually oxygen, to a substrate.        Combustion, many explosives, and organic redox reactions involve        atom-transfer reactions.    -   By the term free radical is meant a molecule (typically highly        reactive and short-lived) having an unpaired valence electron.        Normally, a free radical is any molecular species capable of        independent existence that contains an unpaired electron in an        atomic orbital. The presence of an unpaired electron results in        certain common properties that are shared by most radicals. Many        radicals are unstable and highly reactive. They can either        donate an electron to or accept an electron from other        molecules, therefore behaving as oxidants or reductants.    -   By the term redox potential is meant the measurement of the        tendency of an environment or chemical species to oxidize or        reduce substrates. The redox potential is a measure of the        tendency of a chemical species to acquire electrons from or lose        electrons to an electrode and thereby be reduced or oxidized.        Redox potential is measured in volts (V), or millivolts (mV) and        often represented as Eh. Each species has its own intrinsic        redox potential; for example, the more positive the reduction        potential (reduction potential is more often used due to general        formalism in electrochemistry), the greater the species'        affinity for electrons and tendency to be reduced. In aqueous        solutions, redox potential is a measure of the tendency of the        solution to either gain or lose electrons when it is subjected        to change by introduction of a new species. A solution with a        higher (more positive) reduction potential than the new species        will have a tendency to gain electrons from the new species        (i.e. to be reduced by oxidizing the new species) and a solution        with a lower (more negative) reduction potential will have a        tendency to lose electrons to the new species (i.e. to be        oxidized by reducing the new species). Because the absolute        potentials are next to impossible to accurately measure,        reduction potentials are defined relative to a reference        electrode. Reduction potentials of aqueous solutions are        determined by measuring the potential difference between an        inert sensing electrode in contact with the solution and a        stable reference electrode connected to the solution by a salt        bridge. An aerobic soil, which is an oxidizing environment, has        an Eh of +800 mV; an anaerobic soil, which is a reducing        environment, has a negative Eh which can reach −300 mV. Oxygen        is found in soils at a redox potential of about +800 mV. When        soil is placed in a closed container, oxygen is used by aerobic        organisms as a terminal electron acceptor until all of it is        depleted. As this process occurs, the redox potential of the        soil decreases, and other compounds can be used as terminal        electron acceptors.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andrelevant art and should not be interpreted in an idealized or overlyformal sense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will also be appreciated that the terms and words used in thefollowing description and claims are not limited to the bibliographicalmeanings but are merely used by the inventor to enable a clear andconsistent understanding of the invention. Accordingly, it should beapparent to those skilled in the art that the following description ofexemplary embodiments of the present invention are provided forillustration purpose only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

Included in the description are flowcharts depicting examples of themethodology which may be used to remediate PFAS. In the followingdescription, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions may be loaded onto a computer orother programmable apparatus to produce a machine such that theinstructions that execute on the computer or other programmableapparatus create means for implementing the functions specified in theflowchart block or blocks. These computer program instructions may alsobe stored in a computer-readable memory that can direct a computer orother programmable apparatus to function in a particular manner suchthat the instructions stored in the computer-readable memory produce anarticle of manufacture including instruction means that implement thefunction specified in the flowchart block or blocks. The computerprogram instructions may also be loaded onto a computer or otherprogrammable apparatus to cause a series of operational steps to beperformed in the computer or on the other programmable apparatus toproduce a computer implemented process such that the instructions thatexecute on the computer or other programmable apparatus provide stepsfor implementing the functions specified in the flowchart block orblocks.

Accordingly, blocks of the flowchart illustrations support combinationsof means for performing the specified functions and combinations ofsteps for performing the specified functions. It will also be understoodthat each block of the flowchart illustrations, and combinations ofblocks in the flowchart illustrations, can be implemented by specialpurpose hardware-based computer systems that perform the specifiedfunctions or steps, or combinations of special purpose hardware andcomputer instructions.

Some portions of this specification are presented in terms of algorithmsor symbolic representations of operations on data stored as bits orbinary digital signals within a machine memory (e.g., a computermemory). These algorithms or symbolic representations are examples oftechniques used by those of ordinary skill in the data processing artsto convey the substance of their work to others skilled in the art. Asused herein, an “algorithm” is a self-consistent sequence of operationsor similar processing leading to a desired result. In this context,algorithms and operations involve the manipulation of informationelements. Typically, but not necessarily, such elements may take theform of electrical, magnetic, or optical signals capable of beingstored, accessed, transferred, combined, compared, or otherwisemanipulated by a machine. It is convenient at times, principally forreasons of common usage, to refer to such signals using words such as“data,” “content,” “bits,” “values,” “elements,” “symbols,”“characters,” “terms,” “numbers,” “numerals,” “words”, or the like.These specific words, however, are merely convenient labels and are tobe associated with appropriate information elements.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses of a machine (e.g., a computer) that manipulates or transformsdata represented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs for asystem and a process for PFAS remediation using the disclosed principlesherein. Thus, while particular embodiments and applications have beenillustrated and described, it is to be understood that the disclosedembodiments are not limited to the precise construction and componentsdisclosed herein. Various modifications, changes and variations, whichwill be apparent to those skilled in the art, may be made in thearrangement, operation and details of the method and apparatus disclosedherein without departing from the spirit and scope defined in theappended claims.

A method of remediation of soil/groundwater containing PFAS compoundsand a system in which the method is implemented is herein disclosed.FIG. 1, in combination with FIGS. 2A-2C provide a methodology flow chartof an illustrative system for PFAS remediation.

One aspect of the present invention is the ability to remediate PFASin-situ. FIGS. 2A-2C provide a cutaway view of a typical in-situenvironment contaminated with a high concentration PFAS plume. One ofreasonable skill in the relevant art will appreciate that the PFAS plumeis three dimensional and likely, nonuniform. Accordingly, the depictionshown in FIGS. 2A-2C are illustrative of an environment that may betreated by the present invention rather than of an actual ground/soilsubstructure.

In the present example, a plurality of ground injection points 270traverse a vadose zone 230 prior to reaching a PFAS plume core 210. Thevadose zone, also termed the unsaturated zone, is the part of Earthbetween the land surface and the top of the phreatic zone, the positionat which the groundwater (the water in the soil's pores) is atatmospheric pressure (“vadose” is from the Latin word for “shallow”).Hence, the vadose zone extends from the top of the ground surface to thewater table. Water in the vadose zone has a pressure head less thanatmospheric pressure and is retained by a combination of adhesion(funicular groundwater), and capillary action (capillary groundwater).If the vadose zone envelops soil, the water contained therein is termedsoil moisture. In fine-grained soils, capillary action can cause thepores of the soil to be fully saturated above the water table at apressure less than atmospheric. The vadose zone does not include thearea that is still saturated above the water table, often referred to asthe capillary fringe.

In the example presented in FIGS. 2A-2C the vadose zone 230 transitionsto a zone of fine sand 240 followed a zone of clay 250. The clay zone250, in this example separates the PFAS plume from a zone of course sand260. Groundwater 280 is illustrated as flowing from left to right.Accordingly a dilute PFAS plume 290 is created downstream of the corePFAS plume 210. While the presented strata are illustrative of manygrounds/soil compositions/structures, they clearly may vary and areillustrative, not controlling. Indeed the variance in structure andcomposition of the ground strata is contemplated by the presentinvention and is not limiting as to PFAS remediation techniques andprocesses of the present invention.

With attention to FIG. 1 and FIG. 2B, a desired zone of treatment 220 isfirst selected and demarcated. The presence of organics (contaminants orjust natural organic material), termed “soil oxidant demand” or just“baseline oxidant demand” within the treatment zone is considered as isother oxidizable organic material representing an oxidant sink. This isthe same for a standard chemical oxidation application design. During atypical design of the present invention, soil samples are collected todetermine soil oxidant demand then all the other contaminant oxidantdemands are added on top to arrive at the minimum oxidant load, which isthen doubled or tripled to add a safety factor.

Initial groundwater samples are collected to measure 110 the zero-hourfluoride concentration range, SOD value and pH conditions. Fluoride isgenerally not present at very high concentrations in natural groundwaterbut within a source area or plume core fluoride concentrations likelyvary significantly. This fluoride concentration range is the basal levelfluoride concentration and serves as a control and comparison point forsubsequent measurements of fluoride concentrations in groundwater.Initial pH conditions are used to optimize the injection design andensure that pH conditions are appropriate for PFAS destruction. In theevent that natural pH is caustic, weak acids are injected to reduce pHto within the neutral range. Along with fluoride levels, pH isconstantly monitored throughout. This is followed by measuring and/orcreating the in-situ thermal environment 120 to ensure that thetemperature of the desired zone of treatment is at least 20° C. SODvalue is used to estimate the quantity and ratio of oxidant and metalcatalyst.

According to one embodiment of the present invention neutral to acidicpH conditions are critical to the preferential generation of higherredox potential radicals (SRs) over lower redox potential radicals(HRs). Therefore, the initial pH conditions are adjusted to pH 2.0-3.0to get the maximum extent of PFAS degradation. The pH of the groundwater is monitored from time to time to ensure high degradation rates ofPFAS. SRs can simultaneously oxidize refractory organic matters and PFASpresent in treated zone under optimal reaction conditions.

According to one embodiment of the present invention the requiredtemperature for remediating PFAS compounds is 20 to 60° C. or higher.The in-situ temperature of the treatment zone is achieved and maintainedthrough, in one embodiment, hot water injection. In other embodimentsthe natural ground temperature is greater than 20° C. while in otherembodiments electrical/solar heating elements increase the in-situthermal environment.

Once the in-situ thermal environment is created a first dispersal 130 ofmetal catalyst is injected into the in-situ thermal environment creatinga catalyst rich environment. With a now thermally sufficient, catalystrich environment, an oxidant is thereafter introduced 140. Thisinjection creates optimal reaction conditions wherein the catalyst andthe oxidant within the in-situ thermal catalyst rich environmentinteract, generating high redox potential free-radicals oxidizing PFAScompounds indicated by the release of measurable fluoride. With areaction taking place a target fluoride concentration is calculated 150.The target fluoride concentration is based on observed reaction ratesand normal fluoride concentration in the surrounding environment.

In one embodiment, the PFAS substances are present in thePFAS-contaminated soil in a range of about 0.05 mg/L or 0.05 parts permillion (ppm) or less to about 40 mg/L or 40 ppm or more. In oneembodiment, the PFAS substances are present in the PFAS-contaminatedsoil in an amount of about 10 mg/L or 10 ppm. The molar ratio ofcatalyst to oxidant according to illustrative embodiments of the methodis of the order of 1:10-1:250. In other embodiments of the invention theratio may span 1:50-1:150 or, in yet other embodiments be as narrow as1:150-1:250. A key aspect 300. In one version of the invention the metalcatalyst is substantially regenerated for each cycle of oxidation. Insuch an instance, the groundwater fluoride concentration as well as therate of increase of fluoride concentration is monitored 160 after eachtreatment reaction to confirm PFAS remediation is ongoing. As thereaction takes place additional oxidant is added to the same zone toachieve up to 99.9% reduction in PFAS mass or until no further increasein groundwater fluoride concentration is observed. In another version,additional catalyst is injected to return the treatment zone to itsoriginal state. If at this point the target fluoride concentration hasbeen reached 165 the process can terminate 195 indicative of substantialPFAS remediation. In an instance in which the target fluorideconcentration has not yet been obtained and the rate of change of thefluoride concentration remains positive, additional oxidant 170 may beadded to sustain the generation of free radicals for PFAS remediation.In an instance in which the target fluoride concentration has yet to beachieved yet and the rate of change of concentration is substantiallyzero 175, further oxidant is unlikely to achieve the desired result.Rather additional catalyst is applied 180 to once again interact withthe oxidant and PFAS raising the rate of remediation until the targetfluoride concentration is obtained.

In an embodiment of the invention the metal catalyst may be replenishedin the zone of treatment to achieve higher orders of oxidation reactionafter monitoring the rate of release of fluoride in groundwater.

Changes in the concentration of fluoride is used for determiningsoil/groundwater (in-situ) reacted PFAS concentration within the desiredzone of treatment and to ascertain the requirement of additionaloxidant/catalyst. The incubation time for the degradation of PFAScompounds according to illustrative embodiments of the method includeapproximately 48 to 72 hrs, with complete degradation of PFAS compoundsachieved by subsequent injection of oxidant and/or catalyst as required.One of reasonable skill in the art will appreciate that at eachsuccessive oxidant application, the mass of PFAS destroyed woulddecline. This means that where PFAS concentrations are high, a greatdeal of PFAS mass can be destroyed in a cost-effective manner.Conversely, adding energy to destroy a comparable amount of PFAS in alow-concentration (dilute) plume is less effective.

Sufficient temperature required to achieve an in-situ thermalenvironment for the optimal reaction of oxidant and the metal catalystmay be attained through passive solar heating, or active heatinggenerated by mechanical, electrical or chemical sources in the desiredzone of treatment. In an illustrative embodiment, heating is performedby solar heating or by conductive heat transfer using heater wellsinstalled into the soil. One or more heater wells are installed tocreate a temperature gradient in the soil to establish conductive heattransfer through the soil from the heater wells.

In an embodiment of the present invention, advanced oxidation techniquesfor PFAS have been described. Oxidants used in the disclosed inventioninclude hydrogen peroxide (HP), peroxymonosulfate (PMS) and persulfate(PS). Amongst these oxidants, PS has the highest redox potential of 2.01V compared to HP and PMS. A common feature among these oxidants is theloosely bounded oxygen atoms in the molecule which upon cleavage cangenerate highly oxidizing radical species. Upon activation, theseoxidants produce highly oxidizing radical species such as hydroxylradicals (.OH, HRs), sulfate radicals (SO4.⁻, SRs), and reducing radicalspecies such as superoxide radical anions (O₂.⁻, SRAs). Depending on thepH under which these radicals are produced they may be in the protonatedor deprotonated form. The amount and type of radical species generatedis dependent upon the activation method. For example, the number of SRsgenerated through UV is twice that generated though transition metals asseen in Eqs. x and y.

S₂O₈² + h γ → 2SO₄^(⋅−)(x) S₂O₈²⁻ + Fe²⁺ → SO₄^(⋅−) + SO₄²⁻ + Fe³⁺(y)

Similarly, PMS can be activated using UV to generate both SRs and HRs asseen in Eq. z.

9HSO₅⁻ + hγ → SO₄^(⋅−) + OH^(⋅)(z)

Along with the catalyst and the oxidant, the pH of the aqueous solutionalso plays a key role in the type of radical generated. Under alkalineconditions, PS generates higher amounts of HRs than SRs. Similarly, HPgenerates SRAs under alkaline condition as shown in Eqs. a-c.

$\begin{matrix}\left. {{H_{2}O_{2}} + {Fe}^{3 +}}\rightarrow{{HO}_{2}^{\cdot} + {Fe}^{2 +} + H^{+}} \right. & (a) \\\left. {{H_{2}O_{2}} + {OH}^{\cdot}}\rightarrow{{HO}_{2} + {H_{2}O}} \right. & (b) \\{{{HO}_{2}^{\cdot} + O_{2}^{\cdot -} + {H^{+}pKa}} = 4.8} & (c)\end{matrix}$

Neutral to acidic pH conditions are critical to the preferentialgeneration of higher redox potential radicals (SRs) over lower redoxpotential radicals (HRs). One aspect of the present invention is thatwith a combination of silver+persulfate, pH drops naturally.

In one embodiment of the present invention each radical has a specificpathway of interaction leading to the decomposition of PFAS, e.g., SRsdecompose PFAS through abstraction of an electron from the oxygenpresent in the carboxylic group, meanwhile HRs follow hydrogenabstraction to destabilize the molecule that eventually leads to itsdegradation. For certain PFAS with at least one carbon-hydrogen bondpresent in the molecule, particularly precursors like (6:2FTS), HRs aremore effective than SRs. Although these methods can effectively activatethe oxidants and degrade pollutants, the need for an external energysource greatly reduces the potential for in-situ application. Hence, oneof the most efficient ways of activating an oxidant is through the useof a metal catalyst. A Fenton reaction involves the generation of HRs byactivating HP with dissolved Fe²⁺. Modified Fenton reactions are hereinevolved to use different activators (catalysts) with different oxidants.

In a preferred embodiment of the present invention the best activatorfor PS was silver (I). PS/Fe²⁺ and PS/Co²⁺ were not effective at all,and only PS/Ag⁺ showed noticeable decomposition of PFOA (experimentsconducted with other oxidants such as HP and PMS conjugated with themetals did not show significant decomposition of PFOA. Fe, Co, and Agare the best activators for HP, PMS, and PS, respectively. However, thebest combination of an oxidant and a metal has been observed to dependon target chemicals and reaction conditions. The PMS/Co²⁺ pair has beenused to generate HRs and SRs for the decomposition of polyfluoroalkylsubstances such as 6:2 fluorotelomer sulfonate, but not forperfluoroalkyl ones.

In some embodiments of the present invention, degradation of PFAS usingadvanced oxidation technologies (AOTs) are herein described. There havebeen tremendous efforts to develop technologies for treatment ofextraordinarily stable PFAS in the environment, particularly in water.The present invention exploits destructive methods, (AOTs) using strongoxidizing radicals to decompose PFAS. Radicals, in particular sulfateradicals (SR; SO4′.⁻) and hydroxyl radicals (HR; .OH), are generatedfrom chemical oxidants such as hydrogen peroxide (HP; H₂O₂),peroxymonosulfate (PMS; HSO₅ ⁻), and persulfate (PS; S₂O₈ ²⁻) whenconjugated with transition metals through so-called Fenton-likereactions.

A specific example of a metal that may be utilized in some embodimentsof the present invention is silver, which exhibits a strong potential ascatalyst to facilitate the degradation of PFAS compounds.

Other examples of transition metals that may be used in some embodimentsof the present invention include titanium, platinum, manganese, nickeland iron or a combination of thereof.

FIG. 3 presents a high-level system diagram for PFAS remediationaccording to one embodiment of the present invention. In one embodimentthe PFAS remediation system includes a fluoride sensor 310 to detect andmeasure an initial fluoride concentration in the PFAS plume 210, and thedesired zone of treatment 220. As the remediation is ongoing the sensorrepeatedly checks and reports on the fluoride concentration level withinthe desired treatment zone 220. As PFAS is remediated, fluorideconcentrations within the zone 220 will raise. The rate at whichfluoride concentrations rise will initially be positive until a point atwhich the lack of PFAS causes the rate of increase to stabilize andeventually approach zero, indicating that the reaction has stopped orthat the fluoride concentrations have reached an equilibrium. In otherembodiments of the present invention a pH sensor 380 is included tomonitor acidity of the plume.

The system also includes a thermal device 320 configured to measure thethermal environment of the PFAS plum. As discussed herein the desiredtreatment zone 220 embodying the PFAS plum 210 is preferably greaterthan 20° C. In situations in which the temperature of the treatmentenvironment is less than 20° C. (or some other desired temperature) thethermal device 320 can impart energy to the PFAS plum 210 desiredtreatment zone 220, raising the temperature to a desired level.

The present invention further includes a catalyst dispersing device 330and an oxidant pump 340. Upon determining the scope size of the PFASplum 210 and corresponding desired treatment zone 220, a designatedamount of catalyst is dispersed into the plume. With the thermalenvironment achieved and with the treatment zone 220 enriched withcatalyst, an oxidant is added to generate free radicals.

Included in the system for PFAS remediation is a control module 350comprising, among other things, a processor 360 and a non-transitorystorage media 370 embodying executable instructions. While the fluoridesensor(s) 310, the thermal device, catalyst dispersing device 330 andoxidant pump 340 are physically connected to the PFAS plume 210 anddesired treatment zone 220 they are also communicatively coupled to thecontrol module 350. As data from each sensor/device is collected andrelayed to the control module, the processor, executing variousinstructions, monitors fluoride concentrations and concentration rates,as well as temperature, pH, and the amount(s) of catalyst and oxidantintroduced to the plume.

The present invention creates a treatment environment suitable for thegeneration of free radicals which thereafter bind with and remediate thePFAS molecules. Each of these processes, according to one embodiment ofthe present invention, occurs within an in-situ PFAS plume.

With attention now to FIG. 4, an ex-situ treatment process in whichextracted groundwater is treated in a reactor above ground is shown. Theabove-ground reactor 410 could include a tank or other vessel, as shownin FIG. 4, and could also include a pond, surface impoundment, or anyother water containment structure. As shown in FIG. 4, ex-situ treatmentof the extracted groundwater may include, in some embodiments, treatmentwith one or more of the following reagents: persulfate, and a transitionmetal catalyst. In some particular embodiments, solar heating is used toincrease the reactor temperature to create ambient in-situ thermalenvironment required for the optimal performance of the reagents, whilein other embodiments electrical or other means to create a suitablethermal environment can be used. As with the in-situ process,degradation is initiated by the addition of metal catalyst to thecontaminated water, following by the addition of an oxidant. The releaseof fluoride is monitored as is the rate of change of fluorideconcentrations. The amount of PFAS degraded is assessed by theconcentration of fluoride released into the water as compared to thebaseline level. The addition of oxidant and/or catalyst into the ambientin-situ thermal environment is continued until no further increase influoride concentration is observed in the water indicating lack offurther PFAS remediation.

To illustrate the above-described process and to add clarity to thesystem implementation, consider the following example.

A PFAS contaminated site is identified and demarcated where highconcentration of PFAS is detected in a source area or downgradient plumecore. The PFAS source area, or desired application area, is definedthrough groundwater sampling with a constellation of performancemonitoring wells installed. The starting groundwater fluorideconcentration is measured within the desired zone of treatmentidentifying a baseline value, and baseline pH conditions are confirmedto be lightly acidic to within the neutral range. Baseline ambienttemperature conditions are also defined to determine if heating isrequired to set ambient temperatures at above 20° C. SOD value is workedout which alone or in combination with site characterization data isused to estimate the quantity and ratio of oxidant and catalyst that isto be applied at the contaminated site. Injection wells are installedwithin the defined treatment area at appropriate spacing such thatfluids to be injected will be distributed throughout the definedtreatment area ensuring homogeneity of the reagents. Heating, ifrequired, is applied in the desired treatment area, e.g., throughinjection of solar heated water or some other means, and a solution ofwater containing metal catalyst is injected to establish a metalcatalyst rich condition with appropriate having a suitable temperature.Oxidant is then applied in successive injections of heated watercontaining oxidant to generate free radicals, thereby degrading PFAS inthe desired treatment area. Fluoride concentrations, (and in someinstances Sulfide concentrations) PFAS concentrations, pH, andtemperature are monitored through groundwater sampling betweensuccessive oxidant injections, and oxidant injections are repeated untilthe desired degree of PFAS destruction is achieved.

In one embodiment of the present invention a method to calculate decayand defluorination of PFASs and Perfluorocarboxylic Acids (PFCAs) isbased on the concentration of F⁻ released from the PFAS molecules intothe aqueous solution, the overall defluorination ratio (deF %) isdefined by the following equation.

${{Overall}\mspace{14mu}{deF}\mspace{14mu}\%} = {\frac{{CF} -}{{C\; 0 \times {NC}} - F} = {\frac{{CF} -}{{C\; 0 \times {NC}} - F} = {\frac{{CF} -}{{C\; 0 \times {NC}} - F} = \frac{{CF} -}{{C\; 0 \times {NC}} - F}}}}$

where CF⁻ is the molar concentration of F⁻ ion released in solution, COis the initial molar concentration of the parent PFAS, and NC—F is thenumber of C—F bonds in the parent PFAS molecule. The described methoddetermines a PFAS groundwater concentration within the desired zone oftreatment 220 which can also be used for ascertaining a PFAS soilconcentration within the same zone.

The point of injection in the vadose zone 230 is marked (see FIG. 2A). Afirst injection of hot water or similar energy source is accomplished,when required, to establish an environmental temperature sufficient forremediation. A metal catalyst is inserted followed by an oxidantinitiates a reaction generating high redox potential free-radicals, eq(1), which subsequently oxidize PFAS compounds leading to a decrease ofPFAS concentration. In this reaction, the oxidant is consumed, leavingthe metal catalyst in place (see eq (2 & 3), FIG. 2B.)

$\begin{matrix}\left. {{Ag}^{+} + {S_{2}O_{8}^{2 -}}}\rightarrow{{Ag}^{2 +} + {SO}_{4}^{\cdot -} + {SO}_{4}^{2 -}} \right. & (1) \\\left. {{Ag}^{+} + {SO}_{4}^{\cdot -}}\rightarrow{{Ag}^{2 +} + {SO}_{4}^{2 -}} \right. & (2) \\\left. {{Ag}^{2 +} + {{R{CO}}_{2}H}}\rightarrow{{Ag}^{+} + {R{CO}}_{2}^{\cdot} + H^{+}} \right. & (3)\end{matrix}$

Fluoride is a byproduct of PFAS remediation. A target groundwaterfluoride concentration, generated through a combined destruction of thePFAS in soil and groundwater, is calculated within the desired zone oftreatment. The concentration of PS in the injected solution is fixed, inone embodiment, at 0.005 M as a standard while ranging up to 0.6 M; theconcentration of transition metals such as Ag⁺, Fe⁺, and cobalt (Co²⁺)is set, in one embodiment, at 0.6 mM while ranging up to 1.2 mM in theinjected solution depending upon the SOD values. Reaction temperaturesno less than 20° C., but ranging up to 60° C. in some embodiments ismaintained and controlled through various heating mechanisms. The rangeof homogeneity is wide enough to assure adequate distribution. Whilethere will be concentration gradients with highest concentrations nearthe injection points and lower further away, the variance does notsignificantly alter the ability of the present invention to remediatePFAS.

As the process is ongoing, samples from groundwater are taken. Samplepreparation and analysis are conducted to identify fluorideconcentrations as compared to a baseline value as well as a rate ofchange of fluoride concentrations. Aqueous fluoride ions detached fromPFAS are measured in one embodiment by using a HQ 440D base combinedwith an Intellical ISE F121 electrode. In one embodiment the detectionlimit can be set at 0.02 mg/L with a Hach ionic strength adjuster (ISA)pack being diluted in 5 mL of water. Samples of 0.5 mL are diluted with0.5 mL ISA stock solution prior to analysis. The concentration of PFASremaining in contaminated zone are traced using high-performance liquidchromatography coupled with triple-quadrupole mass spectrometry(LC-MS/MS). Any disappearance of PFAS is ascribed to their chemicaldecomposition. Subsequent additions of heat (to control/maintain thethermal environment) and injections of oxidant and/or catalyst are givento achieve near complete destruction of PFAS in-situ. As a result, thePFAS mass is reduced by >99.9% after successive applications of oxidantand/or catalyst. In most instances, after the reaction the oxidant isdepleted while the metal catalyst remains in-place. The amount of PFASdegraded is assessed by the concentration of fluoride released into thegroundwater and final PFAS concentrations measured in groundwater. Theinjection of oxidant into the ambient in-situ thermal environment iscontinued, in most instances, until no further increase in fluorideconcentration is observed in groundwater, or until the desired degree ofPFAS destruction is achieved.

In one embodiment of the present invention a computer system isprogrammed to process the site characterization data of SOD, pH andtemperature to estimate the quantity and ratio of oxidant and catalyst,which is automatically injected into the desired zone of treatmentthrough the injection wells at the treatment site.

FIGS. 5A-5D show an application of the present invention for treatmentin a surface impoundment/vadose zone soils. In such an application asurface structure or impoundment is recognized have a high PFAS content.Catalysts consistent with the present invention as added to theimpoundment along with an oxidant. In many respects solar energy can beused to raise the impoundment temperature above 20 degrees Celsius. Ininstances in which solar energy is insufficient, hot water can be addedto the impoundment site to render an acceptable thermal environment.

With a sufficient thermal environment established, and with bothcatalyst and oxidant present, remediation of PFAS can begin. Surfacewater application of catalysts and oxidant results in the destruction ofPFAS compounds and generation of fluoride, carbon dioxide, and water.With fluoride concentrations being first measured and thereaftermonitored, the rate and effectiveness of the remediation effort can beascertained. In many instances, greater than 99.9% of PFAS is destroyedwithin 72 hours leaving fluoride and carbon dioxide. As the rate offluoride concentration diminishes, and when the target concentration hasyet to be obtained, additional oxidant can be added. Catalyst andoxidant percolate downward destroying PFAS mass in the vadose zone.Eventually the catalyst and oxidant reach the water table and continueto destroy PFAS mass. Upon reaching a target fluoride concentration,indicative of PFAS remediation, additive oxidant injections can haltleaving the catalyst in place.

FIGS. 6A-6C presents a chart showing decomposition of PFOA at 60° C. bypersulfate (PS) alone and persulfate (PS) in combination with silver(Ag). FIG. 6A shows that oxidant alone (PS) at high temperatures (60°C.) can degrade approximately 90% of PFOA whereas nearly 50%decomposition of PFOA can be achieved by the combination of oxidant (PS)and catalyst (Ag) within 54 hours. As described herein, when thetemperature is reduced the catalyst plays a significant role inactivating the oxidant and generating the radicals capable of degradingPFOA as seen in FIG. 6B. FIG. 6B presents decomposition of PFOA at 40°C. by oxidant (PS) alone and oxidant (PS) in combination with catalyst(Ag).

Lastly, FIG. 6C shows decomposition of PFOA by oxidant in combinationwith catalyst at 40° C. wherein oxidant was continuously injected up to5 times for an incremental decomposition. As seen in FIG. 6C, a singlecatalyst dose was applied and after every 24 hours an oxidant dose wasapplied to achieve nearly 67% decomposition of PFOA. Similarapplications of the processes described herein can be conducted in thepresence of soil wherein PFOA was spiked in the mixed matrix containingwater and soil mixture as seen in FIG. 6D. In one embodiment catalyst isadded once with oxidant applied every 24 hours thereafter up to 140hours for a steady decomposition of PFOA after every oxidant injectionto achieve a final decomposition of approximately 63% over 6 days. Theincrease in decomposition rate of the PFOA from day 5 to day 6 isaligned with a significant reduction of organic matter in soil toovercome the soil oxidant demand due to previous oxidant injections.These results are highly impactful and pertain to PFOA contamination inthe vadose zone and saturated zone soils.

It will also be understood by those familiar with the art, that theinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. Likewise, theparticular naming and division of the modules, managers, functions,systems, engines, layers, features, attributes, methodologies, and otheraspects are not mandatory or significant, and the mechanisms thatimplement the invention or its features may have different names,divisions, and/or formats. Furthermore, as will be apparent to one ofordinary skill in the relevant art, the modules, managers, functions,systems, engines, layers, features, attributes, methodologies, and otheraspects of the invention can be implemented as software, hardware,firmware, or any combination of the three. Of course, wherever acomponent of the present invention is implemented as software, thecomponent can be implemented as a script, as a standalone program, aspart of a larger program, as a plurality of separate scripts and/orprograms, as a statically or dynamically linked library, as a kernelloadable module, as a device driver, and/or in every and any other wayknown now or in the future to those of skill in the art of computerprogramming. Additionally, the present invention is in no way limited toimplementation in any specific programming language, or for any specificoperating system or environment. Accordingly, the disclosure of thepresent invention is intended to be illustrative, but not limiting, ofthe scope of the invention.

In a preferred embodiment, one or more portions of the present inventioncan be implemented in software. Software programming code which embodiesthe present invention is typically accessed by a microprocessor fromlong-term, persistent storage media of some type, such as a flash driveor hard drive. The software programming code may be embodied on any of avariety of known media for use with a data processing system, such as adiskette, hard drive, CD-ROM, or the like. The code may be distributedon such media or may be distributed from the memory or storage of onecomputer system over a network of some type to other computer systemsfor use by such other systems. Alternatively, the programming code maybe embodied in the memory of the device and accessed by a microprocessorusing an internal bus. The techniques and methods for embodying softwareprogramming code in memory, on physical media, and/or distributingsoftware code via networks are well known and will not be furtherdiscussed herein.

An exemplary system for implementing the invention includes ageneral-purpose computing device including a processing unit, a systemmemory, and a system bus that couples various system components,including the system memory to the processing unit. The system bus maybe any of several types of bus structures including a memory bus ormemory controller, a peripheral bus, and a local bus using any of avariety of bus architectures. The system memory generally includesread-only memory (ROM) and random-access memory (RAM). A basicinput/output system (BIOS), containing the basic routines that help totransfer information between elements within the personal computer, suchas during start-up, is stored in ROM. Such a processing device mayfurther include a hard disk drive for reading from and writing to a harddisk, a magnetic disk drive for reading from or writing to a removablemagnetic disk. The hard disk drive and magnetic disk drive are connectedto the system bus by a hard disk drive interface and a magnetic diskdrive interface, respectively. The drives and their associatedcomputer-readable media provide non-volatile storage of computerreadable instructions, data structures, program modules and other datafor the personal computer. It should be appreciated by those skilled inthe art that other types of computer readable media which can store datathat is accessible by a computer may also be used in the exemplaryoperating environment.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the spirit and scope of the invention,as hereinafter claimed.

We claim:
 1. A method for in-situ remediation of per- andpolyfluoroalkyl compounds (PFAS) in a desired zone of treatment, themethod comprising: measuring a groundwater fluoride concentration withinthe desired zone of treatment; verifying an ambient in-situ thermalenvironment within the desired zone of treatment having atemperature >20 degrees centigrade; dispersing a transition metalcatalyst into the ambient in-situ thermal environment creating anambient in-situ thermal catalyst rich environment; introducing, to theambient in-situ thermal catalyst rich environment, an oxidant whereinthe catalyst and the oxidant within the ambient in-situ thermal catalystrich environment interact generating high redox potential free-radicalsoxidizing PFAS compounds producing, inter alia, fluoride; calculating atarget groundwater fluoride concentration generated through PFASdestruction within the desired zone of treatment, and naturallyoccurring groundwater fluoride concentration; monitoring the groundwaterfluoride concentrations and a rate of change of fluoride concentrationwithin the desired zone of treatment; and responsive to the monitoredgroundwater fluoride concentrations being less than the targetgroundwater fluoride concentration in the desired zone of treatment,injecting into the desired zone of treatment additional oxidant.
 2. Themethod of claim 1 wherein the high redox potential free-radicals oxidizeperfluorooctanoic acid (PFOA) in the desired zone of treatment.
 3. Themethod of claim 1, wherein the oxidant is a peroxy-based/sulfur-basedmaterial.
 4. The method of claim 3, wherein the oxidant is persulfate.5. The method of claim 3, wherein the oxidant is hydrogen peroxide. 6.The method of claim 1, wherein the metal catalyst is uniformly dispersedthroughout the desired zone of treatment.
 7. The method of claim 1,wherein the metal catalyst is regenerated for each cycle of oxidation.8. The method of claim 1, wherein the metal catalyst is regenerated uponinteracting with the oxidant.
 9. The method of claim 1, whereinresponsive to the rate of change fluoride concentrations being less thanzero, further dispersing additional catalyst.
 10. The method of claim 1,wherein the metal catalyst is regenerated by decarboxylation of acarboxylic group.
 11. The method of claim 1, wherein the metal catalystis replenished after monitoring the rate of release of fluoride ingroundwater.
 12. The method of claim 1, wherein the PFAS compounds aredestroyed while they are flushed through the vadose zone, therebypreventing groundwater contamination.
 13. The method of claim 1, whereinthe desired zone of treatment includes a material selected from thegroup consisting of a biomass, an organic compound, an inorganiccompound in the form of a solid, and an inorganic compound in the formof an aqueous solution.
 14. The method of claim 1, wherein the molarratio of catalyst to oxidant is of the order of 1:10100-1:1000.
 15. Themethod of claim 1, wherein the ambient in-situ thermal environment is≥20 degrees centigrade and ≤35 degrees centigrade.
 16. The method ofclaim 1, wherein the ambient in-situ thermal environment is ≥20 degreescentigrade and ≤30 degrees centigrade.
 17. The method of claim 1,wherein the ambient in-situ thermal environment is ≥20 degreescentigrade and ≤40 degrees centigrade
 18. The method of claim 1, whereinthe oxidant is consumed after producing free radicals.
 19. The method ofclaim 1, wherein 80% or more of oxidation of PFAS is achieved within 72hrs.
 20. The method of claim 19, wherein the PFAS compound comprise oneor more per- and polyfluorocarboxylic acids or conjugate bases thereof.21. The method of claim 1, further comprising establishing the ambientin-situ thermal environment through passive solar heating of the desiredzone of treatment.
 22. The method of claim 1, further comprisingestablishing the ambient in-situ thermal environment through activeheating generated by mechanical, electrical or chemical sources of thedesired zone of treatment.
 23. A system for in-situ reduction of per-and polyfluoroalkyl compounds (PFAS) in a desired zone of treatment, themethod comprising: a potentiometric sensor configured to measure in-situa groundwater fluoride concentration within the desired zone oftreatment; one or more thermal devices configured to verify an ambientin-situ thermal environment within the desired zone of treatment havinga temperature >20 degrees centigrade; a dispersing device configured todisperse a transition metal catalyst into the ambient in-situ thermalenvironment creating an ambient in-situ thermal catalyst richenvironment; an oxidant pump configured to introduce, to the ambientin-situ thermal catalyst rich environment, an oxidant wherein thecatalyst and the oxidant within the ambient in-situ thermal catalystrich environment interact generating high redox potential free-radicalsoxidizing PFAS compounds producing, inter alia, fluoride; a processorcommunicatively coupled to a non-transitory readable storage mediumtangibly embodying a program of instructions executable by theprocessor, for calculating a target groundwater fluoride concentrationgenerated through PFAS destruction and a rate of change of risingfluoride concentration within the desired zone of treatment, andnaturally occurring groundwater fluoride concentration; monitoring thegroundwater fluoride concentrations and a rate of change of fluorideconcentrations within the desired zone of treatment; and responsive tothe monitored groundwater fluoride concentrations being less than thetarget groundwater fluoride concentration in the desired zone oftreatment, injecting, by the oxidant pump into the desired zone oftreatment, additional oxidant.
 24. The system of claim 23, wherein theoxidant is a peroxy-based/sulfur-based material.
 25. The system of claim24, wherein the oxidant is persulfate.
 26. The system of claim 24,wherein the oxidant is hydrogen peroxide.
 27. The system of claim 24,wherein the oxidant is a combination of oxidants selected from a classconsisting of persulfate and hydrogen peroxide.
 28. The system of claim23, wherein the dispersing device is configured to distribute the metalcatalyst equally throughout the desired zone of treatment.
 29. Thesystem of claim 23, further comprising instructions executable by theprocessor for dispersing additional catalyst to the desired zone oftreatment responsive to the rate of rising fluoride concentrations beingless than zero.
 30. The system of claim 23, wherein the desired zone oftreatment includes a material selected from the group consisting of abiomass, an organic compound, an inorganic compound in the form of asolid, and an inorganic compound in the form of an aqueous solution.